With　the　development　of　cloud　computing,　many　enterprises　have　been　interested　in　outsourcing　their　data　to　cloud　servers　to　decrease　IT　costs　and　rise　capabilities　of　provided　services.　To　afford　confidentiality　and　fine-grained　data　access　control,　attribute-based　encryption　(ABE)　was　proposed　and　used　in　several　cloud　storage　systems.　However,　scalability　and　flexibility　in　key　delegation　and　user　revocation　mechanisms　are　primary　issues　in　ABE　systems.　In　this　paper,　we　introduce　the　concept　of　a　fully　distributed　revocable　ciphertext-policy　hierarchical　ABE　(FDR-CP-HABE)　and　design　the　first　FDR-CP-HABE　scheme.　Our　scheme　offers　a　high　level　of　flexibility　and　scalability　in　the　key　delegation　and　user　revocation　phases.　Moreover,　our　scheme　is　efficient　and　provides　lightweight　computation　in　the　decryption　phase.　Indeed,　by　exploiting　a　computation　outsourcing　technique,　most　of　the　operations　are　executed　by　the　powerful　cloud　server,　and　very　few　computations　are　left　to　the　users.　Also,　the　storage　cost　on　the　user　side　is　significantly　decreased　as　compared　to　similar　schemes.　Furthermore,　using　the　hardness　assumption　of　DBDH　problem,　we　prove　that　our　scheme　is　adaptively　secure　in　the　standard　model.　Our　security　analyses　and　implementation　results　indicate　that　our　scheme　is　efficient,　secure,　and　scalable.　(C)　2020　Elsevier　B.V.　All　rights　reserved.